Represent command completion tags as structs

The backend was using strings to represent command tags and doing string
comparisons in multiple places, but that's slow and unhelpful.  Create a
new command list with a supporting structure to use instead; this is
stored in a tag-list-file that can be tailored to specific purposes with
a caller-definable C macro, similar to what we do for WAL resource
managers.  The first first such uses are a new CommandTag enum and a
CommandTagBehavior struct.

Replace numerous occurrences of char *completionTag with a
QueryCompletion struct so that the code no longer stores information
about completed queries in a cstring.  Only at the last moment, in
EndCommand(), does this get converted to a string.

EventTriggerCacheItem no longer holds an array of palloc’d tag strings
in sorted order, but rather just a Bitmapset over the CommandTags.

Author: Mark Dilger, with unsolicited help from Álvaro Herrera
Reviewed-by: John Naylor, Tom Lane
Discussion: https://postgr.es/m/981A9DB4-3F0C-4DA5-88AD-CB9CFF4D6CAD@enterprisedb.com

1 files changed, 4 insertions, 4 deletions

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index c47be0ba4cd..dbae18d68c6 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -158,12 +158,12 @@ InitPlanCache(void)
  *
  * raw_parse_tree: output of raw_parser(), or NULL if empty query
  * query_string: original query text
- * commandTag: compile-time-constant tag for query, or NULL if empty query
+ * commandTag: command tag for query, or UNKNOWN if empty query
  */
 CachedPlanSource *
 CreateCachedPlan(RawStmt *raw_parse_tree,
 				 const char *query_string,
-				 const char *commandTag)
+				 CommandTag commandTag)
 {
 	CachedPlanSource *plansource;
 	MemoryContext source_context;
@@ -241,12 +241,12 @@ CreateCachedPlan(RawStmt *raw_parse_tree,
  *
  * raw_parse_tree: output of raw_parser(), or NULL if empty query
  * query_string: original query text
- * commandTag: compile-time-constant tag for query, or NULL if empty query
+ * commandTag: command tag for query, or NULL if empty query
  */
 CachedPlanSource *
 CreateOneShotCachedPlan(RawStmt *raw_parse_tree,
 						const char *query_string,
-						const char *commandTag)
+						CommandTag commandTag)
 {
 	CachedPlanSource *plansource;